We are all familiar with the dietary guideline exhorting us to eat so many portions of oily fish per week in order to boost our intakes of n-3 long-chain PUFA, but it is perhaps not so widely realised that the fish must themselves be provided with dietary n-3 long-chain PUFA or, possibly, their precursors (though, as in humans, the ability of carnivorous fish to elongate and desaturate n-3 PUFA appears to be limited)

Younger, Katherine

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Technological University Dublin ARROW@TU Dublin Articles School of Biological Sciences 2008 Editorial: Nutrition Research Reviews Katherine Younger Technological University Dublin, katherine.younger@tudublin.ie Follow this and additional works at: https://arrow.tudublin.ie/scschbioart  Part of the Dietetics and Clinical Nutrition Commons Recommended Citation Younger, K. (2008). Nutrition Research Reviews: Editorial. Nutrition Research Reviews, Access Volume 21, Issue 2, pp. 83-84. doi:10.1017/S0954422408182579 This Article is brought to you for free and open access by the School of Biological Sciences at ARROW@TU Dublin. It has been accepted for inclusion in Articles by an authorized administrator of ARROW@TU Dublin. For more information, please contact yvonne.desmond@tudublin.ie, arrow.admin@tudublin.ie, brian.widdis@tudublin.ie. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License EditorialWe are all familiar with the dietary guideline exhorting us toeat so many portions of oily fish per week in order to boostour intakes of n-3 long-chain PUFA, but it is perhaps not sowidely realised that the fish must themselves be providedwith dietary n-3 long-chain PUFA or, possibly, theirprecursors (though, as in humans, the ability of carnivorousfish to elongate and desaturate n-3 PUFA appears to belimited). In the wild, fish obtain these fatty acids frommarine plankton; however, as Miller et al. (1) here point out,the harvesting of wild fish to meet human requirements isunsustainable. Farmed fish represent a viable alternative,and Miller et al. discuss renewable sources of n-3 PUFA foruse in aquaculture, including other marine creatures such ascopepods, or single-cell organisms such as diatoms thatcould be grown in culture using biotechnological tech-niques, or, more futuristically, land plants geneticallyengineered to produce long-chain PUFA (i.e. 20 and 22C asdistinct from the 18C precursors), which would, ifsuccessful (and acceptable to consumers), be the mostsustainable and cheapest source.Breast milk is the ultimate functional food, containing boththe perfect formulation of nutrients required by the infant(even in the face of the mother’s nutritional inadequacy) anda wide complement of protective components, theseproperties usually being considered in that order. McClellanet al. (2) here invite us to reprioritise these twomajor functionsof breastmilk, citing evidence in their fascinating comparativestudy of five contemporary mammalian species whichsuggests that the secretion that ultimately becamemammalianmilk during the course of evolution started out as a coating thatprotected the (shelled) offspring from desiccation andmicrobial attack, the nutritional role coming later. Strikingly,the nutrients themselves (unique to the mammary gland)appear to have evolved from existing protective and immunemolecules, and are multifunctional, having antimicrobial andother beneficial effects in addition to their nutritive value (forexample, in the case of lactose, its promotion of Ca absorptionand prebiotic effects). Mammalian milk is itself arguablymultifunctional, a range of ingredients being employed indifferent combinations and concentrations in different speciesin such away as to facilitatewidely varying litter sizes, rates ofgrowth and development of offspring. Seemingly, the morethat is discovered about this extraordinary secretion, the moreclear it becomes that mammals should ideally be reared ontheir own mother’s milk.Additional to the above, breast-feeding is also known tohelp protect offspring against obesity, which is nowunderstood to be associated with a state of low-gradeinflammation. The review by Forsythe et al. (3) examinesthe relationship between this obesity-related inflammationand weight loss, concluding that according to the availableevidence, this must be at least 10% in order to be ofbenefit. However, these authors argue that there is a need forbetter-conducted, longer-duration studies, in which malesand females are considered separately, the age range of thesubjects is tightened, both actual and relative body weightchanges are reported, and body fat and lean tissue arecalculated relative to height (as fat mass index and fat-freemass index, respectively), this being far preferable to merelyreporting surrogate measures of adiposity such as BMI orwaist circumference, given that the inflammatory markersare associated with adiposity per se. Taking these tworeviews together, it could be argued that future studiesshould also report on whether and for how long subjectswere breast-fed.Once weaned, children may have access to sugar-sweetened soft drinks, and controversy has long surroundedthe question of whether or not these are responsible forobesity. Sigrid Gibson(4) takes a close look at the evidencefrom observational studies and interventions, and some willbe disappointed to learn that she concludes that the evidenceis inconclusive. Inadequacies in the design and conduct ofmany studies render them less than useful; for example,some don’t distinguish between ‘diet’ and regular softdrinks, or fruit juice, when surveying intakes, and manyhave not considered activity (which might be expected to beassociated with the rate of consumption of soft drinks). Evenin well-conducted studies, it is difficult to compare resultsdue to differences in study design, definitions used,statistical analysis and interpretation of results, though itis possible to deduce that the largest studies report thesmallest effects. Ultimately, in this universe, it is energybalance that determines whether body energy is gained orlost, and soft drinks have a role to play in obesity if theyconstitute a significant source of energy, and if not, not.Furthermore, there is no good evidence to support the notionthat the energy provided from soft drinks is moreobesogenic (even though it might be less nutrient-dense)than energy from other sources.Abdominal obesity is a feature of the metabolicsyndrome, and the review by van Meijl et al. (5) examineswhether this and other features of the syndrome could beprevented by consuming dairy products. Historically, thesehave been somewhat demonised due to their saturated fatcontent; hence the longstanding recommendation, endorsedby these authors, that reduced-fat versions are preferable.On the other hand the other components in dairy productscould be responsible for beneficial effects such as improvedblood-lipid profiles and reduced blood pressure in the caseof Ca, while the satiating effects of protein improve weightloss, while preserving fat-free mass, also improve bloodlipid profiles, and may reduce blood pressure via an effecton angiotensin-1-converting enzyme (ACE) activity (thoughthis last effect has not been shown in humans). While theevidence in favour of dairy products in the prevention andtreatment of the metabolic syndrome is not substantial, itNutrition Research Reviews (2008), 21, 83–84q The Author 2008doi:10.1017/S0954422408182579NutritionResearchReviewshttps://www.cambridge.org/core/terms. https://doi.org/10.1017/S0954422408182579Downloaded from https://www.cambridge.org/core. IP address: 109.77.227.202, on 29 Oct 2020 at 15:25:10, subject to the Cambridge Core terms of use, available atwill be interesting to watch whether further research willprove them to be beneficial and, if so, which components areresponsible.The ability of dietary factors to reduce blood pressure andother CVD risk factors in vivo is also examined in relationto grape products by Pérez-Jiménez & Saura-Caulixo(6), inboth human and animal studies. Grape products containpolyphenols and many other compounds, including alcoholin the case of wine, and it is important to distinguishbetween the effects of these by, for example, using grapejuice or dealcoholised wine in studies. Reassuringly forthose of us who like a drink, alcohol has positive effects onblood pressure and blood lipids separate from those of thepolyphenols, tannins etc, which are also anti-thrombotic,anti-atherosclerotic and, of course, antioxidant. Lack ofconsistency in reporting of the composition of the variouspreparations makes it difficult to compare across studies, butfuture work may prove grape products also to be anti-inflammatory and of benefit in the management of type 2diabetes. Cheers!Cancer is another main scourge of human populations,and we here present two reviews relating to the effects ofdiet in cancer prevention. Thompson et al. (7) investigate therole of trans-fatty acids, hitherto linked with adverse effectson blood lipids but also, perhaps, with cancers of the breast,colon/rectum and prostate, among others; while Vossenaaret al. (8) discuss how concordance with World CancerResearch Fund and American Institute of Cancer Research(WCRF/AICR) dietary and lifestyle recommendations canbe evaluated. Both reviews grapple with problemsassociated with methodologies; in the case of trans-fattyacids, assessment of dietary intake is made difficult by thecontinuous reformulation of margarines and cooking fats bymanufacturers, and the fact that it is not possible to calculatedietary intake from the proportions of trans-fatty acidsmeasured in tissues; meaning that establishing a linkbetween trans fatty acid intakes and cancer risk is notstraightforward thus finding that a relationship with cancerrisk is not straightforward. On the whole, the evidence for anassociation appears weak; the strongest association reported(from the Nurses’ Health Study, for non-Hodgekin’slymphoma) relies on dietary intakes assessed in 1980,which clearly need to be verified by more up-to-date dietaryintake measurements in this population. Very interesting isthe association between trans-fatty acid intakes andincreased risk of prostate cancer among those with aparticular genotype (35% of the population), which theseauthors recommend should certainly be further investigated.They also anticipate that ongoing prospective studies inwhich dietary fat composition is being measured asaccurately as possible will shed further light on the dietaryfat and cancer story. Vossenaar and colleagues take up thevexed question of how one can evaluate whether and to whatextent populations or individuals comply with dietary andlifestyle recommendations, in this case the ones set by theWCRF/AICR for cancer prevention. These authors arguethat selection of appropriate evaluation criteria andassessment methods is key in order to be able usefully torelate such compliance (or the lack of it) with health indices,to help in the identification of population-specific healtheducation targets and to evaluate health interventions.The study of the regulation of energy intake andexpenditure over the last decade has identified a plethoraof signals involved in stimulating, sensing and discontinuingnutrient intake, as well as monitoring the metabolic status ofthe body. This explosion of data is overwhelming, making itdifficult for non-experts to see the overall picture. In thiscontext, the review by Roche et al. (9) is very welcome; itlucidly describes the origins and actions of these signals,providing an integrated picture of how food and nutrientintake is regulated in single-stomached and ruminantanimals. This review beautifully illustrates how researchinto two disparate areas, both of great importance tohumans, that is, human obesity and the optimisation ofruminant animal production, can be of mutual benefit.K. M. YoungerEditor-in-ChiefSchool of Biological SciencesDublin Institute of TechnologyKevin StreetDublin 8Republic of IrelandKatherine.Younger@dit.ieReferences1 Miller MR, Nichols PD & Carter CG (2008) n-3 Oil sources foruse in aquaculture – alternatives to the unsustainable harvest ofwild fish. Nutr Res Rev 21, 85–96.2 McClellan HL, Miller SJ & Hartmann PE (2008) Evolution oflactation: nutrition v. protection with special reference to fivemammalian species. Nutr Res Rev 21, 97–116.3 Forsythe LK, Wallace JMW & Livingstone MBE (2008)Obesity and inflammation: the effects of weight loss. Nutr ResRev 21, 117–133.4 Gibson S (2008) Sugar-sweetened soft drinks and obesity:a systematic review of the evidence from observational studiesand interventions. Nutr Res Rev 21, 134–147.5 van Meijl LEC, Vrolix R & Mensink RP (2008) Dairy productconsumption and the metabolic syndrome. Nutr Res Rev 21,148–157.6 Pérez-Jiménez J & Saura-Calixto F (2008) Grape products andcardiovascular disease risk factors. Nutr Res Rev 21, 158–173.7 Thompson AK, Shaw DI, Minihane AM, et al. (2008) Trans-fatty acids and cancer: the evidence reviewed. Nutr Res Rev 21,174–188.8 Vossenaar M, Solomons NW, Valdéz-Ramos R, et al. (2008)Evaluating concordance with the 1997 World Cancer ResearchFund/American Institute of Cancer Research cancer preventionguidelines: challenges for the research community. Nutr ResRev 21, 189–206.9 Roche JR, Blache D, Kay JK, et al. (2008) Neuroendocrine andphysiological regulation of intake with particular reference todomesticated ruminant animals. Nutr Res Rev 21, 207–234.Editorial84NutritionResearchReviewshttps://www.cambridge.org/core/terms. https://doi.org/10.1017/S0954422408182579Downloaded from https://www.cambridge.org/core. IP address: 109.77.227.202, on 29 Oct 2020 at 15:25:10, subject to the Cambridge Core terms of use, available at

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